Archive for the ‘Green Updates’ Category

From laptops to smartphones to the burgeoning electric car industry, our world is increasingly reliant on rechargeable batteries. But as anyone who’s owned a laptop for more than a few years knows, batteries eventually lose their ability to hold a full charge.

Scientists never really understood why this happens, which has made it a hard problem to fix. But according to a pair of recent studies by researchers from the U.S. Department of Energy, published in the journal Nature Communications, we may be closer than ever to a battery that doesn’t degrade.

Working specifically with lithium-ion batteries, commonly used in consumer devices because of their light weight and high capacity, the scientists have mapped the charge and discharge process down to billionths of a meter to better understand exactly how degradation works. They discovered two culprits in battery degradation. The first: microscopic vulnerabilities in the structure of the battery material steer the lithium ions haphazardly through the cell, eroding the battery in seemingly random ways, much like rust spreads across imperfections in steel. In the second study, focused on finding the best balance between voltage, storage capacity and maximum charge cycles, researchers not only found similar issues with the ion flow, but also tiny accumulations of nano-scale crystals left behind by chemical reactions, which cause the flow of ions to become even more irregular after each charge. Running batteries at higher voltagesalso led to more ion path irregularities, and thus a more rapidly deteriorating battery.

It may seem like scientists should have fully understood the battery—a technology that’s effectively been around since 1800—decades ago. But Huolin Xin, a materials scientist at Brookhaven Lab and coauthor on both studies, says the winning combination of new technologies only recently became available.

“Many state-of-the-art characterization tools, such as aberration-corrected electron microscopes and new synchrotron X-ray techniques, were not available 10 years ago,” Xin says. But now, he says, they can be applied to the study of lithium-ion batteries.

The new data gives researchers a clearer picture of the how these batteries work, which could lead to longer-lasting batteries in consumer electronics in the not-too-distant future. But, it also presents new problems. Xin says maximizing surface area is important to battery performance, but a larger surface area also likely facilitates degradation.

“To prevent [surface degradation], we can either coat the cathode with a protection layer,” Xin says, “or hide these surfaces by creating boundaries within the micron-sized powders [inside the cell].”

Finding the most efficient, cost-effective ways to do this will be part of a future phase of the research.

But Daniel Abraham, a scientist focused on lithium-ion battery research at the Argonne National Laboratory outside Chicago, is skeptical that the new studies represent a real breakthrough. He says mapping work with similar materials has been done in the past, including by his team about 12 years ago. He also believes there may be more to battery degradation than what the new studies have found.

“They’re trying to make a correlation between performance degradation and the pictures that they see, which may not be correct,” Abraham says. “It’s partially the story, but I don’t think it’s the entire story.”

Xin, is more optimistic that the work will lead to battery improvements, not only for future electric vehicles, but for portable electronics as well.

“Lithium-nickel-manganese-cobalt-oxide cathode has recently been identified as the only commercially viable material for next-generation lithium-ion batteries,” Xin says. “By resolving its degradation problem, we can make next-generation batteries smaller and make them charge and discharge more reliably.”

The two battery experts do agree though, that for many important future applications, finding a way to make batteries that don’t wear out as quickly is just as important as creating batteries that have a greater capacity.

Xin points out that electric car buyers justifiably worry about battery failure after their warranty expires. Abraham notes that while you likely only need a couple of years of performance from your smartphone or tablet battery, for electric vehicles, most owners are looking for a battery that lasts 10 to 15 years. And for use in the electric grid (to store excess energy produced on off-peak hours), batteries should last 30 years or more.

That makes building a better battery for your laptop a lot easier than solving longevity problems in other areas.

“It’s good to have a higher energy density, but if you get a high energy density but not a long life, then the commercial viability of those technologies comes into question,” Abraham says. “Whereas, if you can show that you have a new technology and it can last between two and 30 years, that becomes immediately viable commercially.”

While the work of Xin and his colleagues may help researchers create batteries that don’t degrade as quickly, it’s clear that further breakthroughs will be necessary before we’ll see rechargeable batteries that last a decade or more without serious wear.

A team of Indian engineers has designed a prototype low-cost solar-heated water desalination unit that can produce about five litres of drinking water each day and is intended for use by rural households.

The desalination unit may be used to turn brackish groundwater fit for drinking at any place with abundant solar energy, the team of engineers, who are from the National Institute of Technology in Kurukshetra and an engineering college in Bangalore, have said.

The laboratory-scale desalination unit they have built and tested in Bangalore produces five litres of drinking water on a sunny day and costs less than Rs 7,000, the engineers said.

More drinking water may be extracted in regions with greater sunshine and if the glass surface collecting solar energy is increased. The engineers described their design in the journal Current Science, published by the Indian Academy of Sciences, last week.

“This is a start — we wanted to see whether this idea works,” said Praveen Hunashikatti, a Bangalore-based team member who had worked on the project while doing his MTech at NIT Kurukshetra. “It looks promising but needs to be improved.”

Over 70 per cent of India’s estimated 600,000 villages use groundwater as their main source of drinking water, drawing it through pumps or wells. But much of this groundwater is brackish and contaminated with metallic ion impurities, from fluorides and nitrates to arsenic.

A report from the Central Ground Water Board, released in 2010, had documented that salt levels in groundwater from over 60 per cent of India’s landmass were beyond human taste limits.

Desalination units based on the reverse osmosis technology have already been installed in some rural areas, but reverse osmosis requires a steady supply of electricity and also generates waste water.

There are also solar-heated desalination units that use parabolic dishes that automatically change their orientation as the sun’s position changes through the day.

“Parabolic dishes that track the sun and change their orientation are expensive and unlikely to be affordable by average rural households,” said Kambalipura R. Suresh, professor of civil engineering at the BMS College of Engineering, Bangalore, and another team member.

The prototype from the Kurukshetra-Bangalore team will need to be scaled up to match the efficacy of the solar-heated desalination units that use parabolic dishes.

Hunashikatti calls the prototype a “coupled system” — a glass collector and a set of long tubes with air evacuated from them to avoid loss of heat. The slope of the glass collector and the orientation of the evacuated tubes are tailored to the latitude of the location.

The desalination is based on conventional distillation —evaporation and condensation. The solar energy, Hunashikatti explained, heats the water, which causes layers of hot water to move upward, evaporate and condense on the glass from where it can be extracted.

“This coupled system is our alternative to automatic tracking — instead of chasing the sun, we orient the slope and the tubes to retain maximum heat,” Suresh told The Telegraph.

A larger glass slope will mean more solar radiation and increase the amount of water generated.

In laboratory tests, the prototype was able to reduce the levels of fluorides, chlorides, nitrates, calcium carbonate, magnesium carbonate, and calcium in samples of water to levels below the acceptable limits for drinking water.

“A scaled-up version will need to be tested at multiple locations for different groundwater and sunshine conditions,” said Basavaraju Prathima, an environmental engineer at the BMS College and a team member.

With the help of photosynthesis plants convert light energy to chemical energy. This chemical energy is stored in the bonds of sugars they use for food. Photosynthesis happens inside a chloroplast. Chloroplasts are considered as the cellular powerhouses that make sugars and impart leaves and algae a green hue. During photosynthesis water is split into oxygen, protons and electrons. When sunrays fall on the leaves and reach the chloroplast, electrons get excited and attain higher energy level. These excited electrons are caught by proteins. The electrons are passed through a series of proteins. These proteins utilize more of the electrons’ energy to synthesize sugars until the entire electron’s energy is exhausted.

Now researchers at Stanford are inspired by a new idea. They intercepted the electrons just after they had been excited by light and were at their highest energy levels. They put the gold electrodes inside the chloroplasts of algae cells, and tapped the electrons to create a tiny electrical current. It may be the beginning of the production of “high efficiency” bioelectricity. This will be a clean and green source of energy but minus carbon dioxide.

Stanford University researchers got their work published in the journal Nano Letters (March, 2010). WonHyoung Ryu is the main author of this work. He says, “We believe we are the first to extract electrons out of living plant cells.” The Stanford research team created an exclusive, ultra-sharp gold nanoelectrode for this project.

They inserted the electrodes inside the algal cell membranes. The cell remains alive throughout the whole process. When cells start the photosynthesis, the electrodes attract electrons and produce tiny electric current. Ryu tells us, “We’re still in the scientific stages of the research. We were dealing with single cells to prove we can harvest the electrons.” The byproducts of such electricity production are protons and oxygen. Ryu says, “This is potentially one of the cleanest energy sources for energy generation. But the question is, is it economically feasible?”

Ryu himself provides the answer. He explained that they were able to extract just one picoampere from each cell. This quantity is so little that they would require a trillion cells photosynthesizing for one hour just to get the same amount of energy in a AA battery.

Another drawback of such an experiment is that the cells die after an hour. It might be the small trickles in the membrane around the electrode could be killing the cells. Or cells may be dying because they’re not storing the energy for their own vital functions necessary to sustain life. To attain commercial viability researchers have to overcome these hurdles.

They should go for a plant with larger chloroplasts for a larger collecting area. For such experiment they will also need a bigger electrode that could tap more electrons. With a longer-surviving plant and superior collecting ability, they could harness more electricity in terms of power.